1 /* Function return value location for Linux/TILE-Gx ABI.
2 Copyright (C) 2012 Tilera Corporation
3 Copyright (C) 2014 Red Hat, Inc.
4 This file is part of elfutils.
5
6 This file is free software; you can redistribute it and/or modify
7 it under the terms of either
8
9 * the GNU Lesser General Public License as published by the Free
10 Software Foundation; either version 3 of the License, or (at
11 your option) any later version
12
13 or
14
15 * the GNU General Public License as published by the Free
16 Software Foundation; either version 2 of the License, or (at
17 your option) any later version
18
19 or both in parallel, as here.
20
21 elfutils is distributed in the hope that it will be useful, but
22 WITHOUT ANY WARRANTY; without even the implied warranty of
23 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
24 General Public License for more details.
25
26 You should have received copies of the GNU General Public License and
27 the GNU Lesser General Public License along with this program. If
28 not, see <http://www.gnu.org/licenses/>. */
29
30
31 #ifdef HAVE_CONFIG_H
32 # include <config.h>
33 #endif
34
35 #include <assert.h>
36 #include <dwarf.h>
37
38 #define BACKEND tilegx_
39 #include "libebl_CPU.h"
40
41
42 /* r0. */
43 static const Dwarf_Op loc_intreg[] =
44 {
45 { .atom = DW_OP_reg0 }
46 };
47 #define nloc_intreg 1
48
49 /* The return value is a structure and is actually stored in stack space
50 passed in a hidden argument by the caller. But, the compiler
51 helpfully returns the address of that space in r0. */
52 static const Dwarf_Op loc_aggregate[] =
53 {
54 { .atom = DW_OP_breg0, .number = 0 }
55 };
56 #define nloc_aggregate 1
57
58 int
tilegx_return_value_location(Dwarf_Die * functypedie,const Dwarf_Op ** locp)59 tilegx_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
60 {
61 /* Start with the function's type, and get the DW_AT_type attribute,
62 which is the type of the return value. */
63 Dwarf_Die die_mem, *typedie = &die_mem;
64 int tag = dwarf_peeled_die_type (functypedie, typedie);
65 if (tag <= 0)
66 return tag;
67
68 Dwarf_Word size;
69 switch (tag)
70 {
71 case -1:
72 return -1;
73
74 case DW_TAG_subrange_type:
75 if (! dwarf_hasattr_integrate (typedie, DW_AT_byte_size))
76 {
77 Dwarf_Attribute attr_mem, *attr;
78 attr = dwarf_attr_integrate (typedie, DW_AT_type, &attr_mem);
79 typedie = dwarf_formref_die (attr, &die_mem);
80 tag = DWARF_TAG_OR_RETURN (typedie);
81 }
82 /* Fall through. */
83
84 case DW_TAG_base_type:
85 case DW_TAG_enumeration_type:
86 case DW_TAG_pointer_type:
87 case DW_TAG_ptr_to_member_type:
88 {
89 Dwarf_Attribute attr_mem;
90 if (dwarf_formudata (dwarf_attr_integrate (typedie, DW_AT_byte_size,
91 &attr_mem), &size) != 0)
92 {
93 if (tag == DW_TAG_pointer_type || tag == DW_TAG_ptr_to_member_type)
94 size = 8;
95 else
96 return -1;
97 }
98 if (tag == DW_TAG_base_type)
99 {
100 Dwarf_Word encoding;
101 if (dwarf_formudata (dwarf_attr_integrate (typedie, DW_AT_encoding,
102 &attr_mem),
103 &encoding) != 0)
104 return -1;
105 }
106 }
107
108 /* Small enough structs are passed directly in registers R0 ... R7. */
109 if (size <= 8)
110 {
111 intreg:
112 *locp = loc_intreg;
113 return nloc_intreg;
114 }
115
116 /* Else fall through. */
117 case DW_TAG_structure_type:
118 case DW_TAG_class_type:
119 case DW_TAG_union_type:
120 aggregate:
121 *locp = loc_aggregate;
122 return nloc_aggregate;
123
124 case DW_TAG_array_type:
125 case DW_TAG_string_type:
126 if (dwarf_aggregate_size (typedie, &size) == 0 && size <= 8)
127 {
128 if (tag == DW_TAG_array_type)
129 {
130 Dwarf_Attribute attr_mem, *attr;
131 /* Check if it's a character array. */
132 attr = dwarf_attr_integrate (typedie, DW_AT_type, &attr_mem);
133 typedie = dwarf_formref_die (attr, &die_mem);
134 tag = DWARF_TAG_OR_RETURN (typedie);
135 if (tag != DW_TAG_base_type)
136 goto aggregate;
137 if (dwarf_formudata (dwarf_attr_integrate (typedie,
138 DW_AT_byte_size,
139 &attr_mem),
140 &size) != 0)
141 return -1;
142 if (size != 1)
143 goto aggregate;
144 }
145 goto intreg;
146 }
147 goto aggregate;
148 }
149
150 /* XXX We don't have a good way to return specific errors from ebl calls.
151 This value means we do not understand the type, but it is well-formed
152 DWARF and might be valid. */
153 return -2;
154 }
155